DESCRIPTION: This is a case-control study designed to collect preliminary data on the relationship between semen quality and serum PCBs, as well as information on the distribution of potential confounders, including chlorinated pesticides, lead, cadmium, and lifestyle factors. Male partners of couples seeking infertility diagnosis at the MGH Infertility Clinics, referred for a first semen analysis, and between 20-45 years of age, are eligible for enrollment. Cases are those with abnormal semen analysis by WHO criteria and may fall into any of 3 categories: 1) concentration less than 20 million spermatozoa/ml; 2) less than 50% motile sperm or less than 10 million total motile spermatozoa; 3) less than 4% normal morphology. Controls do not meet all three case group criteria. Blood samples, obtained immediately after semen donation, will be analyzed for 65 individual PCB congeners, DDE, HCB and Pb; urine samples will be analyzed for cadmium level. A self-administered questionnaire will obtain data on additional potential confounders for both life-time and the 3 months preceding semen donation. Multiple logistic regression models will assess the relationship between serum PCBs and each case definition.